Disconnect mechanism for a tandem axle system

ABSTRACT

A vehicle includes a tandem axle system having an inter-axle differential and clutching assembly, a forward or first axle assembly, and a rear or second axle assembly. The inter-axle differential and clutching assembly includes a differential mechanism having first and second side gears and a clutch mechanism having a clutch member and an actuator assembly. At least one of the first axle assembly and the second axle assembly is in selective driving engagement with the inter-axle differential and clutching assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

The present patent application claims the benefit of Indian ProvisionalPatent Application No. 201911001062, filed Jan. 9, 2019, and U.S.Provisional Patent Application No. 62/815,455, filed Mar. 8, 2019, whichare fully incorporated herein by reference in their entirety

BACKGROUND

Conventional tandem axle systems have two drivable axles for a vehicle.Such tandem axle systems typically include either 6×4 drivelines (i.e.two wheels on a steer axle and four driving wheels on a pair of tandemaxles behind the steer axle) or 6×2 drivelines (i.e., two wheels on thesteer axle and four wheels on the tandem axles behind the steer axlewhere only two wheels are on a drive axle). The 6×2 drivelines are oftenundesirable since they lack the required tractive effort under poortraction conditions. However, the 6×4 drivelines are also undesirablebecause under most driving traction coefficient conditions, two driveaxles are not required to develop the necessary tractive effort for atruck, such as a Class 8 truck, Additionally, the 6×4 drivelines can becostly and heavy.

At startup, on grades, at low speeds, during backup maneuvering, or inother environments where additional traction is needed, it would bebeneficial to operate a tandem vehicle in a 6×4 mode. However, as thetandem vehicle nears a predetermined speed or condition where lesstraction is required, operating the tandem vehicle in a 6×2 mode is moredesirable as it increases efficiency.

In view of the disadvantages of the known prior art systems, it would beadvantageous to develop a tandem axle system that allows a tandemvehicle to selectively operate in both the 6×2 and 6×4 modes.

SUMMARY

In concordance and agreement with the present disclosure, a tandem axlesystem that allows a tandem vehicle to selectively operate in both a 6×2mode and a 6×4 mode, has surprisingly been discovered.

In one embodiment of the present disclosure, a tandem axle systemcomprises: a first axle assembly; a second axle assembly; and aninter-axle differential and clutching assembly coupled to at least oneof the first axle assembly and the second axle assembly, wherein theinter-axle differential and clutching assembly includes an inter-axledifferential having a differential mechanism and a clutch mechanism,wherein the differential mechanism includes a first side gear drivinglyconnected to one of the first and second axle assemblies, and a secondside gear disposed about a pinion drivingly connected to of one of thefirst and second axle assemblies, and wherein the clutch mechanismincludes a movable clutch member disposed on the pinion and configuredto selectively engage the second side gear.

As aspects of certain embodiments, at least one of the first axleassembly and the second axle assembly includes a plurality of axle halfshafts.

As aspects of certain embodiments, the differential mechanism furtherincludes a bearing disposed between the second side gear and the pinion.

As aspects of certain embodiments, the clutch member is in splinedengagement with the pinion.

As aspects of certain embodiments, the second side gear includes aplurality of first teeth and a plurality of second teeth formed thereon.

As aspects of certain embodiments, the clutch member includes aplurality of teeth formed thereon.

As aspects of certain embodiments, the teeth of the clutch memberselectively engages the first teeth formed on the second side gear.

As aspects of certain embodiments, the second teeth of the second sidegear are in meshed engagement with at least one pinion gear of thedifferential mechanism.

As aspects of certain embodiments, the differential mechanism is atleast partially disposed in a housing.

As aspects of certain embodiments, the inter-axle differential furtherincludes an inter-axle differential lock.

As aspects of certain embodiments, the inter-axle differential lockselectively engages the housing of the differential mechanism.

As aspects of certain embodiments, the inter-axle differential lockincludes a main body having a plurality of teeth formed thereon.

As aspects of certain embodiments, the main body of the inter-axledifferential lock is disposed about the second side gear.

As aspects of certain embodiments, the teeth of the main body of theinter-axle differential lock selectively engages a plurality of teethformed on a housing of the differential mechanism.

As aspects of certain embodiments, the inter-axle differential furtherincludes an actuator assembly configured to selectively engage anddisengage at least one of the clutch mechanism and the inter-axledifferential lock.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages, will become readily apparent tothose skilled in the art from the following detailed description whenconsidered in the light of the accompanying drawings in which:

FIG. 1 is a top view a portion of a vehicle including a tandem axlesystem having an inter-axle differential and clutching assembly, aforward or first axle assembly, and a rear or second axle assemblyaccording to an embodiment of the presently described subject matter;

FIG. 2 is a front perspective view of the inter-axle differential andclutching assembly of the tandem axle system shown in FIG. 1 accordingto an embodiment of the presently described subject matter;

FIG. 3 is a rear perspective view of the inter-axle differential andclutching assembly of the tandem axle system shown in FIG. 1;

FIG. 4 is a front perspective view of a first housing portion of theinter-axle differential and clutching assembly shown in FIGS. 1-3according to an embodiment of the presently described subject matter;

FIG. 5 is a front perspective view of a second housing portion of theinter-axle differential and clutching assembly shown in FIGS. 1-3according to an embodiment of the presently described subject matter;

FIG. 6 is a rear perspective view of the second housing portion of theinter-axle differential and clutching assembly shown in FIGS. 1-3 and 5according to an embodiment of the presently described subject matter;

FIG. 7 is a cross-sectional view of a portion of the inter-axledifferential and clutching assembly shown in FIGS. 1-3 according anembodiment of the presently described subject matter, wherein aninter-axle differential lock is shown in a first or disengaged positionand a clutch mechanism for axle disconnect is shown in a first orengaged position;

FIG. 8 is an enlarged cross-sectional view of a portion of theinter-axle differential and clutching assembly shown in FIGS. 1-3according an embodiment of the presently described subject matter,wherein the inter-axle differential lock is shown in the first ordisengaged position and the clutch mechanism for axle disconnect isshown in the first or engaged position;

FIG. 9 is a cross-sectional view of a portion of the inter-axledifferential and clutching assembly shown in FIGS. 1-3 according anembodiment of the presently described subject matter, wherein theinter-axle differential lock is shown in a second or engaged positionand the clutch mechanism is shown in a second or disengaged position;

FIG. 10 is an enlarged side perspective view, partially in section, of aportion of the inter-axle differential and clutching assembly shown inFIGS. 1-3 according to an embodiment of the presently described subjectmatter;

FIG. 11 is a partially exploded side perspective view of a portion ofthe inter-axle differential and clutching assembly shown in FIGS. 1-3according to an embodiment of the presently described subject matter;

FIG. 12 is a perspective view of a through-shaft of the inter-axledifferential and clutching assembly shown in FIGS. 7-9 according to anembodiment of the presently described subject matter;

FIG. 13 is a perspective view of a second side gear of an inter-axledifferential mechanism of the inter-axle differential and clutchingassembly shown in FIGS. 7-11 according to an embodiment of the presentlydescribed subject matter;

FIG. 14 is a perspective view of a movable clutch member of the clutchmechanism of the inter-axle differential and clutching assembly shown inFIGS. 7-11 according to an embodiment of the presently described subjectmatter; and

FIG. 15 is a perspective view of an actuator of an actuator assembly ofthe inter-axle differential and clutching assembly shown in FIGS. 7-11according to an embodiment of the presently described subject matter.

DETAILED DESCRIPTION

It is to be understood that the system may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions, directions or other physical characteristics relating to theembodiments disclosed are not to be considered as limiting, unless theclaims expressly state otherwise.

FIG. 1 illustrates a vehicle 10 including a tandem axle system 100according to an embodiment of the presently described subject matter.The tandem axle system 100 may be drivingly connected to a transmission(not depicted). The transmission may be drivingly connected to an engineof the vehicle 10 or other source of rotational power. In certainembodiments, the transmission can be, but is not limited to, anautomated manual transmission, a dual clutch transmission, an automatictransmission or a manual transmission.

The tandem axle system 100 shown includes an inter-axle differential andclutching assembly 102, a forward or first axle assembly 104, and a rearor second axle assembly 106. The first axle assembly 104 and the secondaxle assembly 106 are in selective driving engagement with theinter-axle differential and clutching assembly 102. Although the axleassemblies 104, 106, as illustrated, are substantially similar in sizeand shape, it is understood that the axle assemblies 104, 106 may havedifferent sizes and shapes depending on the functions assigned to each,if desired.

In certain embodiments, the first axle assembly 104 may include a set ofaxle half shafts 104 a, 104 b and a differential assembly (not depicted)drivingly connected thereto. Similarly, the second axle assembly 106 mayinclude a set of axle half shafts 106 a, 106 b. As shown in FIGS. 2-3,the inter-axle differential and clutching assembly 102 may include afirst housing portion 103 and a second housing portion or carrier 105.Various shapes, sizes, and configurations may employed for each of thehousing portions 103, 105 such as the embodiments of the first housingportion 103 shown in FIG. 4 and the second housing portion 105 shown inFIGS. 5-6. As a non-limiting example, the housing portions 103, 105 arecoupled to each other by a plurality of fasteners 101. It is understood,however, that any suitable means of coupling the housing portions 103,105 together may be employed such as by mechanical and non-mechanicalmethods, if desired. It should be appreciated that additional housingportions may be employed or the housing portions 103, 105 may beintegrally formed as a unitary component if desired.

As illustrated in FIGS. 7-9, the inter-axle differential and clutchingassembly 102 may further include an inter-axle differential (IAD) 108disposed within the housing portions 103, 105. In certain embodiments,the IAD 108 includes a differential mechanism 107 disposed within ahousing 109 and a clutch mechanism for axle disconnect 110. In someembodiments, the differential mechanism 107 in the housing 109 ispositioned within the housing position 103 and the clutch mechanism foraxle disconnect 110 is at least partially positioned within both thehousing portions 103, 105.

The IAD 108 is configured to divide a torque received from an input orsource of torque (not depicted) between the first axle assembly 104 andthe second axle assembly 106. It should be appreciated that the IAD 108may be used for other purposes and applications as desired. In certainembodiments, the torque is transferred from a driveline transmission ofthe vehicle 10 to the IAD 108 through an input shaft 112 formed with thehousing 109. It is understood that the input shaft 112 may be integrallyformed with the housing 109 or as a separate and distinct component.

In the embodiment shown in FIGS. 7-9, the differential mechanism 107 ofthe IAD 108 may include a first side gear 120, an opposing second sidegear 122, and a pair of opposing pinion gears 124, 125. Additionalpinion gears (not depicted) may be employed as desired. In certainembodiments, the pinion gears 124, 125 may be coupled to the housing 109via respective pinion shaft 127, 128. The pinion shafts 127, 128 may beconfigured to transfer the torque from the housing 109 of the IAD 108 tothe pinion gears 124, 125. As illustrated, the first side gear 120 maybe arranged to transfer the torque from the pinion gears 124, 125 to athrough-shaft 130 (depicted in FIG. 12). In certain embodiments, thefirst side gear 120 is disposed concentrically about the through-shaft130 and coupled thereto for rotation therewith. Various methods ofcoupling the first side gear 120 to the through-shaft 130 may beemployed such as by a splined engagement, for example. In certainembodiments, the through-shaft 130 may also be drivingly connected tothe rear axle assembly 106.

As shown, the second side gear 122 of the differential mechanism 107 maybe arranged to selectively transfer the torque from the pinion gears124, 125, through the clutch mechanism for axle disconnect 110, to ahollow pinion 140 disposed concentrically about the through-shaft 130.In some embodiments, as shown in FIG. 13, the second side gear 122 has aset of first teeth 146 formed on a first surface 122 a and a set ofsecond teeth 147 formed on an opposing second surface 122 b. As anon-limiting example, the first teeth 146 of the second side gear 122are configured to selectively mesh with the clutch mechanism for axledisconnect 110 and the second teeth 147 of the second side gear 122 areconfigured to mesh with a set of teeth (not depicted) formed on each ofthe pinion gears 124, 125. In certain embodiments, the second side gear122 is mounted on a stem of the pinion 140 along with at least onebearing such as a needle roller bearing, for example, to allow freerotation about the pinion 140.

In certain embodiments, the clutch mechanism for axle disconnect 110includes a movable clutch member 150 and an actuator assembly 151. Theclutch member 150 is configured to selectively engage and disengage withthe second side gear 122. In certain embodiments, both of the secondside gear 122 and the clutch member 150 are disposed concentricallyabout the pinion 140 and coupled thereto for rotation therewith. Variousmethods of coupling the second side gear 122 and the clutch member 150to the pinion 140 may be employed such as by a splined engagement, forexample. In certain embodiments, the clutch member 150 is coupled to thepinion 140 by a splined engagement to permit the clutch member 150 totranslate axially along a longitudinal axis of the pinion 140.

As more clearly shown in FIG. 9, the clutch member 150 is rotatablymounted on the stem of the pinion 140. In certain embodiments, a set ofsplines (not depicted) on a radially inner surface 153 of the clutchmember 150 may be engaged with a set of splines (not depicted) on aradially outer surface 154 of the stem of the pinion 140. A set of teeth155 (illustrated more clearly in FIG. 14) is formed on an axial end ofthe clutch member 150 to selectively engage with the teeth 146(illustrated more clearly in FIG. 13) formed on the second side gear120. The clutch mechanism for axle disconnect 110 is axially movablealong the stem of the pinion 140 by the actuator assembly 151 as shownin FIGS. 7-11 to selectively engage and disengage the second side gear120. In some embodiments, the clutch mechanism for axle disconnect 110selectively connects the IAD 108 to axle half shafts 104 a, 104 b of theforward axle assembly 104 through the pinion 140. In certainembodiments, the actuator assembly 151 is used to position the clutchmechanism for axle disconnect 110.

As a non-limiting example, the actuator assembly 151 may be a shift forkassembly using a pneumatic shifting mechanism to position the shiftfork. It should be appreciated, however, that various other types ofactuator assemblies may be employed as the actuator assembly 151 ifdesired. In certain embodiments, the actuator assembly 151 includes anactuator 158 (i.e. a shift fork shown in FIG. 15). In some embodiments,the actuator 158 may be connected to an axial first end 159 of a pushrod 160 by a nut 162. In other embodiments, the actuator 158 may beconnected to the push rod 160 by any suitable method as desired. Asshown, the actuator 158 is disposed at least partially about an outercircumferential surface of the clutch member 150. The actuator 158,depicted in FIG. 15, may include a first portion 164 and an opposingsecond portion 166. As a non-limiting example, the portions 164, 166 ofthe actuator 158 may be received into an annular groove 168, moreclearly illustrated in FIG. 9, formed in the clutch member 150. In otherembodiments, the actuator 158 may positioned adjacent the clutch member150 opposite the second gear 120.

Referring now to FIG. 10, the push rod 160 may have an axial second end170 disposed in a cavity 171 formed in the second housing portion 105.As illustrated, the push rod 160 may also have a biasing member 172surrounding an outer surface of the push rod 160 inside the cavity 171of the second housing portion 105. A cap 174 is disposed on the secondend 170 of the push rod 160 to limit an axial movement of the push rod160 within the cavity 171 of the second housing portion 105.

In certain embodiments, the IAD 108 may further include an inter-axledifferential lock 176 configured to selectively engage and disengagewith the housing 109. As a non-limiting example, the inter-axledifferential lock 176 is in a first or disengaged position when theclutch mechanism for axle disconnect 110 is in a first or engagedposition, as shown in FIGS. 7 and 8, and the inter-axle differentiallock 176 is in a second or engaged position when the clutch mechanismfor axle disconnect 110 is in a second or disengaged position, as shownin FIG. 9. As more clearly illustrated in FIG. 10, the inter-axledifferential lock 176 may include a main body 178 having a set of teeth180 formed on an axial end surface and an annular groove 182 formed inan outer circumferential surface thereof. In the embodiment shown inFIG. 11, the teeth 180 may be configured to mesh with a set of teeth 181formed on an end surface of the housing 109 of the IAD 108 for rotationtherewith when the inter-axle differential lock 176 is in the first orengaged position.

In one embodiment, the inter-axle differential lock 176 may be caused tobe selectively engaged and disengaged by an actuator assembly 177. As anon-limiting example, the actuator assembly 177 may be a shift forkassembly using a pneumatic shifting mechanism to position the shiftfork. It should be appreciated, however, that various other types ofactuator assemblies may be employed as the actuator assembly 177 ifdesired. In certain embodiments, the actuator assembly 177 includes anactuator 183 (i.e. a shift fork more clearly shown in FIG. 10). In someembodiments, the actuator 183 may be connected to an axial first end 186of a push rod 184 by a nut 185. In other embodiments, the actuator 183may be connected to the push rod 184 by any suitable method as desired.As shown, the actuator 183 is disposed at least partially about an outercircumferential surface of the main body 178 of the inter-axledifferential lock 176. The actuator 183 may include a first portion (notdepicted) and a spaced-apart opposing second portion (not depicted). Asa non-limiting example, the portions of the actuator 183 may be receivedinto the annular groove 182, more clearly illustrated in FIG. 10, formedin the main body 178. Referring now to FIG. 10, the push rod 184 mayhave an axial second end (not depicted) disposed in a cavity 179(depicted in FIG. 6) formed in the second housing portion 105. A biasingmember (not depicted) may be surround an outer surface of the push rod184 inside the cavity 179 of the second housing portion 105. A cap (notdepicted) may be disposed on the second end of the push rod 184 to limitan axial movement of the push rod 184 within the cavity 179 of thesecond housing portion 105. In another embodiment, the inter-axledifferential lock 176 may be caused to be selectively engaged anddisengaged with the housing 109 by the actuator assembly 151, therebyemploying only a single actuator assembly 151 for the IAD 108.

Referring now to FIG. 1, the rear axle assembly 106 may include adifferential assembly 200. The differential assembly 200 is drivinglyconnected to a set of axle half shafts 106 a, 106 b of the rear axleassembly 106. It should be appreciated that the differential assembly200 may be any suitable differential assembly 200 as desired.

In some embodiments, the vehicle 10 may also include a control system(not depicted). The control system allows an operator of the vehicle 10and/or the controller to control the tandem axle system 100. The controlsystem includes at least one controller and one or more sensors or asensor array. The sensors can be intelligent sensors, self-validatingsensors and smart sensors with embedded diagnostics. The controller isconfigured to receive signals and communicate with the sensors. The oneor more sensors are used to monitor performance of the tandem axlesystem 100. The sensors can collect data from the driveline of thevehicle including, but not limited to, the torque and rotational speedof at least one of the axle half shafts 104 a, 104 b, 106 a, 106 b. Thespeed of rotation and the torque are indicative of the speed of rotationand torque of the engine. In one embodiment, the sensors are mountedalong at least one of the axle half shafts 104 a, 104 b, 106 a, 106 b,but can also be mounted elsewhere on the vehicle 10. In one embodiment,the control system includes additional discrete sensors beyond sensorsalready included in other components of the vehicle.

The control system can also include a vehicle communication datalink incommunication with the sensors and the controller. The sensors generatesignals that can be directly transmitted to the controller ortransmitted via the datalink or a similar network. In one embodiment,the controller can be integrated into an existing controller system inthe vehicle including, but not limited to, an engine controller, atransmission controller, etc. or can be a discrete unit included in thecontrol system. The controller may communicate a vehicle communicationdatalink message (comm. link J1939 or the like) to other components ofthe driveline including, but not limited to, the engine.

In one embodiment, the controller is an electrical control unit (ECU).The ECU herein can be configured with hardware alone, or to runsoftware, that permits the ECU to send, receive, process and store dataand to electrically communicate with sensors, other components of thedriveline or other ECUs in the vehicle. Additionally, the controller caninclude a microprocessor. The microprocessor is capable of receivingsignals, performing calculations based on those signals and storing datareceived from the sensors and/or programmed into the microprocessor. Thecontrol system allows an operator of the vehicle 10 and/or thecontroller to control the tandem axle system 100. In some embodiments,the control system includes an axle control unit in communication withthe clutch mechanism for axle disconnect 110.

In some embodiments, the control system receives signals noting thevehicle 10 is moving above predetermined speed or condition and send asignal to the clutch mechanism for axle disconnect 110 to disconnect thefront axle assembly 104 by disengaging the clutch member 150 from thesecond side gear 122.

In operation, when a 6×4 mode of the vehicle 10 is desired, the clutchmechanism for axle disconnect 110 is caused to move to the first orengaged position in which the clutch member 150 engages with the secondside gear 122 and the inter-axle differential lock 176 is caused to moveto the first or disengaged position in which the main body 178disengages from the housing 109 of the IAD 108, the torque flows fromthe second side gear 122 to the pinion 140 of the front axle assembly104 and the vehicle configuration changes from the 6×2 mode to the 6×4mode as shown in FIGS. 7 and 8.

When a 6×2 mode of the vehicle 10 is desired, the clutch mechanism foraxle disconnect 110 is caused to move to the second or disengagedposition in which the clutch member 150 disengages from the second sidegear 122 and the inter-axle differential lock 176 is caused to move tothe second or engaged position in which the main body 178 engages withthe housing 109 of the IAD 108, the torque from the input shaft 112 isdisconnected from the second side gear 122 of the IAD 108 of the frontaxle assembly 104 and the vehicle configuration changes from the 6×4mode to the 6×2 mode as shown in FIG. 9.

The foregoing description details certain embodiments. It will beappreciated, however, that no matter how detailed the foregoing appearsin text, the preferred embodiments can be practiced in many ways. As isalso stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the preferredembodiments should not be taken to imply that the terminology is beingre-defined herein to be restricted to including any specificcharacteristics of the features or aspects of the embodiments with whichthat terminology is associated.

While preferred embodiments have been shown and described herein, itwill be obvious to those skilled in the art that such embodiments areprovided by way of example only. Numerous variations, changes, andsubstitutions will now occur to those skilled in the art withoutdeparting from the preferred embodiments. It should be understood thatvarious alternatives to the embodiments described herein may be employedin practice. It is intended that the following claims define the scopeof the preferred embodiments and that methods and structures within thescope of these claims and their equivalents be covered thereby.

What is claimed is:
 1. A tandem axle system comprising: a first axleassembly; a second axle assembly; an inter-axle differential andclutching assembly coupled to at least one of the first axle assemblyand the second axle assembly, wherein the inter-axle differential andclutching assembly includes an inter-axle differential having adifferential mechanism and a clutch mechanism, wherein the inter-axledifferential includes an inter-axle differential lock, wherein thedifferential mechanism is at least partially disposed in a housing andincludes a first side gear drivingly connected to one of the first andsecond axle assemblies, and a second side gear disposed about a piniondrivingly connected to a remaining one of the first and second axleassemblies, and wherein the clutch mechanism includes a movable clutchmember disposed on the pinion and configured to selectively engage thesecond side gear.
 2. The tandem axle system of claim 1, wherein at leastone of the first axle assembly and the second axle assembly includes aplurality of axle half shafts.
 3. The tandem axle system of claim 1,wherein the differential mechanism further includes a bearing disposedbetween the second side gear and the pinion.
 4. The tandem axle systemof claim 1, wherein the clutch member is in splined engagement with thepinion.
 5. The tandem axle system of claim 1, wherein the second sidegear includes a plurality of first teeth and a plurality of second teethformed thereon.
 6. The tandem axle system of claim 5, wherein the clutchmember includes a plurality of teeth formed thereon.
 7. The tandem axlesystem of claim 6, wherein the teeth of the clutch member selectivelyengages the first teeth formed on the second side gear.
 8. The tandemaxle system of claim 5, wherein the second teeth of the second side gearare in meshed engagement with at least one pinion gear of thedifferential mechanism.
 9. The tandem axle system of claim 1, whereinthe inter-axle differential lock selectively engages the housing of thedifferential mechanism.
 10. The tandem axle system of claim 1, whereinthe inter-axle differential lock includes a main body having a pluralityof teeth formed thereon.
 11. The tandem axle system of claim 10, whereinthe main body of the inter-axle differential lock is disposed about thesecond side gear.
 12. The tandem axle system of claim 11, wherein theteeth of the main body of the inter-axle differential lock selectivelyengages a plurality of teeth formed on the housing of the differentialmechanism.
 13. The tandem axle system of claim 1, wherein the inter-axledifferential further includes an actuator assembly configured toselectively engage and disengage at least one of the clutch mechanismand the inter-axle differential lock.